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Diseases that can be Transmitted by Mosquitoes

While mosquitoborne disease is not as common in Minnesota as it is in tropical climates, there are several diseases that may occur within the state. Minnesota residents who travel to other countries can also return with tropical diseases such as malaria or dengue.

West Nile Virus (WNV)
West Nile virus is a disease transmitted to people, horses, and birds. It is the most commonly reported mosquitoborne disease in Minnesota. Most people infected with West Nile virus show no symptoms or flu-like symptoms, but some (primarily elderly) have more severe illness. West Nile virus was found in Minnesota in 2002 and will remain a public health concern in the foreseeable future.

La Crosse Encephalitis (LAC)
La Crosse encephalitis is a viral disease that is transmitted by the Tree Hole mosquito. It has been responsible for an average of 4-5 cases each year in Minnesota, primarily involving severe illness in children.

Jamestown Canyon Virus (JCV)
Jamestown Canyon virus, which may be transmitted by several different species of mosquitoes throughout Minnesota, is a rarely reported cause of illness in humans. The virus is closely related to La Crosse virus, although disease is reported less frequently and any age group may be affected.

Western
Equine Encephalitis (WEE)
Western Equine Encephalitis is a disease transmitted to people, horses, and birds. It is caused by a virus that is transmitted by the same mosquito species that commonly transmits WNV in western Minnesota. During 1941, there was a large regional outbreak of Western equine encephalitis. In more recent years, Minnesota has had infrequent and smaller outbreaks of WEE (15 human cases in 1975, single cases in 1983 and 1999).

Eastern
Equine Encephalitis (EEE)
Eastern equine encephalitis is a rare illness in humans and horses, and only a few cases are reported in the United States each year. Many people infected with EEE virus show no symptoms but some (primarily children) have severe illness. Although cases have been reported in horses, no human cases have been identified in Minnesota.

St.
Louis Encephalitis (SLE)
CDC; Cases of St. Louis encephalitis are usually the result of unpredictable
and intermittent localized epidemics. SLE has not been reported in Minnesota since the 1970’s. Attention:
Non-MDH link

Mosquitoborne Diseases Affecting Travelers

Minnesota residents who travel to other countries or certain areas of the southern United States can return with mosquitoborne diseases such as malaria, dengue, chikungunya, yellow fever, and zika virus. People who travel to other areas of the world may be at risk and should be familiar with the symptoms of these diseases. Medications used to prevent infection are available for malaria and vaccines are currently available for yellow fever. Avoidance of mosquito bites and use of mosquito repellent are recommended when traveling to affected areas. For more information on international travel, visit International Travel & Infectious Disease.

Chikungunya
CDC; Chikungunya virus is primarily found in Africa and Asia yet was found in 2013 for the first time in the Western Hemisphere. Attention: Non-MDH link

Dengue
CDC; Dengue fever is primarily a tropical disease and rarely occurs within the continental United States. In recent years, Dengue has occurred in southern states, including Texas and Florida. Attention: Non-MDH link

Malaria
CDC; Malaria is still a public health concern in North America even though local exposure to the disease hasn’t occurred in nearly 100 years. Attention: Non-MDH link

Yellow Fever
CDC; Yellow fever virus is a rare tropical illness in Minnesota travelers with vaccination being one of the most important steps in prevention. Attention: Non-MDH link

Zika Virus
Zika virus has been responsible for outbreaks in tropical areas throughout the world and was found in 2015 for the first time in the Western Hemisphere.